RFR: 8024671: G1 generates assert error messages in product builds

[Aleksey Shipilev]

Hi,

Please review and push this simple change:
  http://cr.openjdk.java.net/~shade/8024671/webrev.00/

TL;DR: err_msg() is not getting erased in product builds, because
check_card_num is not a macro, causing the performance regression. Turns
out it is simpler to inline the check_card_num all along, because it is
more consistent to other asserts.

Testing:
  (the change is trivial, so the testing is limited)
  - built on Linux x86_64/{release,fastdebug}
  - run the targeted microbenchmark Linux x86_64/{release,fastdebug}

Thanks,
-Aleksey.